This invention relates to rotary mechanisms such as rotary engines, compressors, or pumps, and, more particularly, to improved spring assemblies employed in biasing seals used in such mechanisms.
Single biasing springs for rotary mechanism seals, frequently known as energizng or backup springs, are conventionally employed in such mechanisms today. One difficulty posed by the use of single springs is that the same often lose their pre-load due to one or the other, or both, of high stress conditions and high operating temperatures.
Stresses are high since every effort is made to reduce the spring rate of the spring so that the pre-load of such springs on the seals will not vary appreciably during engine operation as the seals move into and out of the grooves. In addition, if the spring load rate is not minimized, manufacturing tolerances are too close, particularly for relatively long springs, to the point where they cannot be economically, reliably manufactured.
Operating temperatures are frequently high, particularly when the rotary mechanism is a rotary engine, for the reason that the seals are exposed to combustion gases. Frequently, the spring assemblies are similarly exposed when the seals are of the so-called gas energized variety.
Moreover, in all types of such rotary mechanisms, temperatures are relatively high because of the greater friction energy absorbed by the seals during operation than would typically be present in, for example, a reciprocating device employing piston rings as seals.